In Pat. No. 3,232,678, issued Feb. 1, 1966 to William G. Wilson, and assigned to the assignee of the present application, there is shown and described a brake control valve device that is substantially the same in function and operation as the brake control valve device included in the standard fluid pressure brake apparatus now in use on railway freight cars owned and operated by American railroads. The brake control valve device shown in the above-mentioned U.S. Pat. No. 3,232,678 comprises a service valve portion embodying therein a plurality of slide, spool and disc type valves, and an emergency valve portion that has a slide-type emergency valve slidable on a flat ported valve seat and a graduating valve slidably mounted on a flat ported surface provided therefor on the side of the emergeny slide valve opposite the side thereof that engages the flat ported valve seat. This emergency valve portion is operative in response to a service rate or reduction of pressure in a train brake pipe to release fluid under pressure from a quick action chamber to atmosphere at a service rate thereby rendering this emergency valve portion effective to cause an emergency brake application only in response to an emergency rate of reduction of pressure in the train brake pipe.
The manufacture and production of these slide-type valves and valve seats of this emergency valve portion require considerable accurate and skillful machining which, as is readily apparent, increases the cost of the emergency valve portion of which they are an essential component.
According,y it is the general purpose of this invention to provide a railway car brake control valve device with a novel emergency valve portion that embodies a first movable abutment, subject on its respective opposite sides to pressure in a train brake pipe and in a quick action chamber that is effective, upon a service rate of reduction of the pressure in the train brake pipe, to unseat a poppet-type valve from one of two coaxial spaced-apart valve seats between which it is disposed so that, while unseated from both valve seats, fluid under pressure is released at a service rate from the quick action chamber, one side of the first abutment and both sides of a second abutment, operatively connected to a combined emergency and brake pipe vent valve, to atmosphere simultaneously as the pressure in the train brake pipe is reduced at a service rate thereby preventing an emergency brake application. Upon an emergency rate of reduction of the pressure in the train brake pipe, the pressure of the fluid in the quick action chamber and acting on the one side of the first abutment shifts the poppet valve into seating engagement with the other valve seat to cut off flow of fluid under pressure from the quick action chamber and one side of the second abutment to atmosphere. The trapped fluid under pressure in the quick action chamber and acting on the one side of the second abutment then deflects this abutment to shift the combined emergency and brake pipe vent valve to a position in which fluid under pressure is released from the brake pipe at an emergency rate rate to cause an emergency brake application and an emergency reservoir is connected to a brake cylinder.